Setting up a technologically advanced installation, such as a ground system, a submarine, etc., represents an enormous investment on the part of the owner, who, to safeguard his investment, often requests that the manufacturer or installation firm also provide for high-level, long-term servicing of the installation. In fact, it is not unusual for a technologically advanced installation to continue operating well past its time, e.g. even 40 years after it is installed, thanks to continual technological updating of the original installation structure.
Servicing an installation normally comprises:                repairs;        spare parts supply;        customized installation programming and updating;        running the installation;        training of installation technicians;        integration with the owner's existing equipment or servicing procedures.        
Servicing involves working in collaboration with installation technicians, which means devising, in conjunction with installation technicians, appropriate processes to maximize efficiency and prompt service, and to keep track of the work carried out and the equipment installed, so that the exact configuration of the installation is known at all times. In other words, the manufacturer or installation firm must maintain full control over the servicing chain, in the sense of knowing exactly the configuration of the installation and the availability of spare parts and servicing material.
A computer network is a definite and indispensable aid to all aspects of servicing work, by constructing and maintaining a centralized data bank constituting an inventory of parts and elementary units (LRU—“Logic Replaceable Unit”) of which the installation is composed. A centralized data bank, however, is only effective to the extent that the data in it is correct, updated and reliable.
The parts and elementary units of an installation are identified using various identification systems, one of the cheapest of which is based on the use of bar codes. More specifically, an unequivocal bar code is assigned to each part and each elementary unit in the installation, and is normally printed on a label applied to the respective installation part or elementary unit.
A bar code system, however, is not the best or most efficient solution to the above problems, for the following main reasons:                the enormous number of references involved, and the complex, variable, and, very often, unique nature of the elementary units associated with the references; a bar code system therefore calls for continually producing and applying different labels, and for appropriate printers, thus increasing running costs (labels, ribbons, maintenance).        in non-industrial environments, reading bar code labels is intentional, and is therefore performed manually by the operator on a portable terminal;        remote bar code reading is only possible using highly complex systems (multiple or robotized readers);        bar codes are read sequentially (one at a time), so that inventories take longer;        a bar code has no memory, the only information being the code reading, which is decoded by access to the data bank; and        to be changed, a bar code label must be physically replaced.        
The drawbacks of the bar code system can be eliminated using a known RFid (“Radio Frequency Identification”) system, which is based on the use of radiofrequency tags known as “tag transponders” or, more simply, “transponders”, which are applied to respective elementary units for identification.
As shown in FIG. 1, a transponder 101 typically comprises a microchip 102 having an electronic memory (not shown); and a normally miniaturized antenna 103. In actual use, transponder 101 is excited, via antenna 103, by the electromagnetic field generated by an external (fixed or portable) RFid read/write device 104, with which it dialogues by radio, and to which it returns the identification code and/or any other information memorized in microchip 102. The external RFid read/write device 104 is normally connectable to a computer device 105 for collecting the identification code and/or any other memorized information.
Transponder 101 also comprises a capacitor (not shown), in which case, transponder 101 is passive, or a small battery (not shown), in which case, transponder 101 is active. Transponder 101 may also be rewritable, for remote programming with additional data, or for complete reprogramming with a new “identity”.
FIG. 2 shows a few examples of transponders 101 of different sizes, which depend on performance requirements, and on the size of the elementary units to which they are applied.
RFid technology provides for solving almost all the drawbacks of bar codes, in that each transponder:                identifies a respective part or elementary unit of the installation with an unequivocal code memorized in its microchip, and is capable of acquiring and memorizing additional data and making it available substantially in real time;        is of the desired shape and size, and can be covered with appropriate material for the type of operation involved;        can be reused, in production or logistics, to perform an infinite number of read/write operations;        unlike bar code labels, can be used in any environment, i.e. in the presence of dirt, water, detergents, paint, chemical solvents, and high temperature;        is readable even when concealed, in inaccessible conditions, free-handedly, and unattended;        is recommended when the respective installation part or component is “followed” by additional data, and so involves memorizing and/or reading data relating, for example, to work progress, maintenance work carried out, tracking, product tracing or authentication (imitation prevention : cannot be photocopied); and        prevents theft, with the provision of appropriate security thresholds.        
Notwithstanding all this, inventory work is hampered, and inventory data made outdated, by a whole host of installation configuration changes that are difficult to trace. Outdated inventory data, in particular, can be attributed to the type of installation and the maintenance work carried out, for example:                remote installation that cannot be moved for reasons of security or non-stop service;        emergency configuration repairs and changes;        configuration changes made by installation operatives without informing the Service Department;        inaccessible installation, e.g. stationed in military or reserved areas.        
Moreover, the RFid identification system is affected by transponder read noise—particularly in the case of passive transponders—caused by numerous situations, in which the magnetic component of the electromagnetic field generated by the RFid read/write device is distorted or attenuated to the point of drastically reducing the energy absorbed by the transponder antenna. More specifically, transponder reading is disturbed by:                reflection of the electromagnetic field on metal walls or walls made of electrically conducting material in the vicinity of the transponder (“echo” effect);        distortion of the electromagnetic field flux lines, caused by the presence of metal or electrically conducting material in the vicinity of the transponder;        the presence of pole fluids (such as distilled water) which absorb the magnetic component; and        stray capacitances introduced by metal walls of installation parts or elementary units, to which the transponder is fitted.        
The presence of metal in the vicinity of the transponder, in particular, impairs the signal/noise S/N ratio of the transponder to the extent of making the transponder unsuitable for use close to electronic circuits, which greatly increase ambient electromagnetic noise.